I'd have to think that insulating the face of the ice from the settlement's air temperature isn't that killer an issue. A settlement with reactors and waste heat anyway could keep a huge volume at a very comfortable temperature. Reactors could be located in the rock a short distance away.

Keeping the habitats warm is not what I am concerned about. Dumping waste heat while making sure the ice won't melt is the engineering challenge IMO. That would require the ice surface to be exposed and temperatures well below freezing. People do enjoy winter temperatures and snow and ice. Though some caves may be isolated and kept warm so plants can grow.

Technical solutions to dissipate low temperature heat energy would be complex and may be prone to failure. Better to have a naturally stable system.

Having some green to walk throug is nice to have. But light for plants would introduce a lot of heat that needs to be dissipated. I am not thinking of growing much food there but plants that need little light as a public park. Plants like ferns and philodendron. Plus a few separately lighted spots for plants that grow fruit like strawberries.

If you want a naturally stable system you can also live in, nothing on Mars will do...

Seriously, you will have to manage your temperatures (by cooling or heating) just as your atmosphere and everything else. This is true for spacecraft, for space stations as the ISS and also will be the case on Mars. Dissipating heat isn't easier in surface structures than in caves in rock or ice. In fact ice at -50°C allows dumping quite a lot of heat into it without the ice melting, making this easier than on the surface where you have to use radiators to get rid of it just like at the ISS.

In fact the ISS with its 450 tons of pressure vessels, structure, airlocks, solar panels, heat exchangers etc. for 6 people is very similar to what you would need to land on Mars for a similar habitat on the surface. Transporting pressure vessels to Mars or building them on Mars just doesn't scale and the fact that you DO have solid material like ice or rock where you can carve out your habitats is a major resource on Mars compared to empty space. And once you have set up your machinery for cutting through ice or rock you can expand for a long time.

And of course at some point you would need to grow plants (and maybe fish) for food. Either that or have all your food imported from Earth forever.

If you want a naturally stable system you can also live in, nothing on Mars will do...

Seriously, you will have to manage your temperatures (by cooling or heating) just as your atmosphere and everything else. This is true for spacecraft, for space stations as the ISS and also will be the case on Mars. Dissipating heat isn't easier in surface structures than in caves in rock or ice. In fact ice at -50°C allows dumping quite a lot of heat into it without the ice melting, making this easier than on the surface where you have to use radiators to get rid of it just like at the ISS.

Yes, of course it will need heating. But with energy consumption inside the living quarters and good isolation not much.

What I mean with naturally stable is the heat flow from habitat to ice being in a range where you don't need technical intervention to keep the temperature outside the habitat and within the ice cave in a practical range. As that cave would have pressure and breathable atmosphere you can vent excess heat by opening the window like you do on earth. Just size habitat size and total energy consumption and size of the ice cave so you don't need active cooling for the cave.

If you want a naturally stable system you can also live in, nothing on Mars will do...

Seriously, you will have to manage your temperatures (by cooling or heating) just as your atmosphere and everything else. This is true for spacecraft, for space stations as the ISS and also will be the case on Mars. Dissipating heat isn't easier in surface structures than in caves in rock or ice. In fact ice at -50°C allows dumping quite a lot of heat into it without the ice melting, making this easier than on the surface where you have to use radiators to get rid of it just like at the ISS.

Yes, of course it will need heating. But with energy consumption inside the living quarters and good isolation not much.

What I mean with naturally stable is the heat flow from habitat to ice being in a range where you don't need technical intervention to keep the temperature outside the habitat and within the ice cave in a practical range. As that cave would have pressure and breathable atmosphere you can vent excess heat by opening the window like you do on earth. Just size habitat size and total energy consumption and size of the ice cave so you don't need active cooling for the cave.

Yes, over all of your habitat this should be the goal, since heat you have to remove is wasted energy. But your habitat will not be just one big cave, it will have lots of rooms and tunnels and water tanks and whatever, with some parts (storage, living quarters) only generating little heat and others (machinery, greenhouses) generating a lot, so you will have to have loops of water pipes to move the heat around from places where's too much of it (cooling them) to other places where's too little of it (heating them).

In the ideal case all of this cancels out, but I guess it will be very, very hard to plan this. Total energy consumption will not be static anyway. So you will have to have the capability to dump heat somewhere to get rid of it and also to generate heat at times where you don't generate enough.

Opening the window will be a bad idea though, losing precious oxygen and nitrogen would be bad.

So a roof of 27m thick clear ice would be self supported with 1 atm pressure inside. The roof would let natural light in. Of course if you had an air leak the roof would collapse. Is there any plants that grow at -10C?

EDIT:Possibly little green houses so the plants can be kept warm. Up here in new hampshire they do little crop row greenhouses about 4 feet wide and 3 feet high. Just enough to keep plants warm in the winter.

Probably gone to need some sort of air conditioner to make sure excess heat doesn't melt the glacier. But air conditioning is easy...

« Last Edit: 10/13/2016 03:00 PM by rsdavis9 »

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With ELV best efficiency was the paradigm. The new paradigm is reusable, good enough, and commonality of design.Same engines. Design once. Same vehicle. Design once. Reusable. Build once.

Opening the window will be a bad idea though, losing precious oxygen and nitrogen would be bad.

The whole cave would be pressurized. And soon, if not immediately, filled with breathable air. There will be plenty of it available from fuel ISRU. Oxygen because the engines run fuel rich and the production is stochiometric. Nitrogen or a breathable mix of oxygen and argon are just a byproduct of extracting the CO2 for the Sabatier process.

Its major industrial products are caustic soda and chlorine, and is used in many industrial processes including the manufacture of polyvinyl chloride, plastics, paper pulp and many other products. Of the annual global production of around two hundred million tonnes of salt, only about 6% is used for human consumption.

Let's see how much salt would be in a large body of water. If it is from precipitation, virtually none. If it is an ancient ocean it may be more. But the oceans of earth have accumulated their salt content over billions of years from rivers. The liquid oceans of Mars did not exist that long at all. I expect that it would still even pass as drinking water, except for possible poisonous ingredients.

Let's see how much salt would be in a large body of water. If it is from precipitation, virtually none. If it is an ancient ocean it may be more. But the oceans of earth have accumulated their salt content over billions of years from rivers. The liquid oceans of Mars did not exist that long at all. I expect that it would still even pass as drinking water, except for possible poisonous ingredients.

Don't know about salt, but the water on Mars is 5 times more enriched in deuterium than Earth water, probably through loss of hydrogen in the upper atmosphere. Venus water has 200 times the concentration of Earth. Water was probably liquid on Mars for quite some time, so quite a bit of leaching should have taken place, followed by evaporation.I expect there might me very salty plains, where the water evaporated rather than froze?

Opening the window will be a bad idea though, losing precious oxygen and nitrogen would be bad.

The whole cave would be pressurized. And soon, if not immediately, filled with breathable air. There will be plenty of it available from fuel ISRU. Oxygen because the engines run fuel rich and the production is stochiometric. Nitrogen or a breathable mix of oxygen and argon are just a byproduct of extracting the CO2 for the Sabatier process.

Yes, the atmosphere being 96% CO2, 2% nitrogen and 2% argon (roughly) means you will accumulate quite a bit of both. Still, to replenish your internal atmosphere you will have to store them in high pressure vessels. In the long run you'll have reserves, but for quite a while having a nice atmosphere in your habitats will be too precious to vent them. Also nitrogen is important for plants, you'll tend to not waste it.

One thing about living on Mars will be that wasting anything will be a bad thing. You'll be fighting an uphill battle against entropy all the time. Finding ways to manage things with minimal losses will be paramount.

(Actually this will be a good thing. Finding ways to deal with all this as a matter of fact on Mars will mean that you will be able to use all of this on Earth to, living without actually wasting things and destroying the eco-systems. The Martians will teach the Earthlings lessons they need to learn anyway.)

90 percent of the glacier-cave talk here sounds like it's been lifted strait from the Zygote settlement of the Mars Trilogy. The notion that a cave itself can be a pressure vessel is deeply flawed, the rock that a glacier sits on can easily be fractured and allow air to escape, as the habitat air is warm it can cause sub-surface melting, likewise the interior air in the cave would have to be kept away from the ice roof to prevent all the issues I described earlier.

The net effect is that your going to need to have a full top and bottom pressure envelope inside the cave, it can be thin because it dose not need protection from micrometeorites as it would exposed on the surface but the cave is really not doing anything that a architectural dome and a few meters of regolith couldn't do, and it has disadvantages too, susceptibility to creep over time, difficulty in dumping waste heat as have been mentioned, inability to use skylights or any other top-down access to the habitat area. Probably most important is that it requires that you not perform simple surface mining of the same glacier body that your living in so as to avoid damaging your own habitat.

Construction on the surface with arches, vaults, columns and other compression load bearing structures can provide the necessary radiation protection without any of these issues. The same thin membrane pressure vessels inflated inside these protected spaces will be necessary but this is unavoidable and a wash. Also note that some posters have erroneously claimed that a single massive pressure vessels is more efficient then many small ones, this is a common error in thinking that the pressure vessel mass scales only with surface area, in actuality it scales with volume due to a large vessel needing a thicker wall. Given the inherent danger, I would say death-trap-ishness, in a single pressure vessel the interconnecting of many individual pressure vessels is certainly the way to go.

Note that a livable habitat is going to consist of a LOT more mass in equipment, life-support and otherwise beyond the pressure vessel, even a pressure vessel made 100 percent from local materials will need nearly the same amount of vital equipment to shipped in. This is the flaw in most space-cadet style housing solutions, they pretend that they are making log cabins in which just walls and roof are all that's needed and that they are saving 90 percent of the shipment mass from Earth.

Which concept would take less total labor and energy to construct for equivalent pressurized volume and level of radiation protection?

1. carving a cave out of a cliffside at a location chosen for the ideal rock properties for carving, or 2. building "temple structures" consisting of columns and arches on a flat plain and covering them with regolith.

Yes, the atmosphere being 96% CO2, 2% nitrogen and 2% argon (roughly) means you will accumulate quite a bit of both. Still, to replenish your internal atmosphere you will have to store them in high pressure vessels. In the long run you'll have reserves, but for quite a while having a nice atmosphere in your habitats will be too precious to vent them. Also nitrogen is important for plants, you'll tend to not waste it.

It seems we have a misunderstanding. I am not suggesting wasting anything. We have a large habitat with breathable air. We have a house that is not pressurized by itself because it does not need to be. Opening the window exchanges air with the larger cave which is closed. Nothing is wasted unless you see pressurizing a large cave with breathable air is waste.

90 percent of the glacier-cave talk here sounds like it's been lifted strait from the Zygote settlement of the Mars Trilogy. The notion that a cave itself can be a pressure vessel is deeply flawed, the rock that a glacier sits on can easily be fractured and allow air to escape, as the habitat air is warm it can cause sub-surface melting, likewise the interior air in the cave would have to be kept away from the ice roof to prevent all the issues I described earlier.

The net effect is that your going to need to have a full top and bottom pressure envelope inside the cave, it can be thin because it dose not need protection from micrometeorites as it would exposed on the surface but the cave is really not doing anything that a architectural dome and a few meters of regolith couldn't do, and it has disadvantages too, susceptibility to creep over time, difficulty in dumping waste heat as have been mentioned, inability to use skylights or any other top-down access to the habitat area. Probably most important is that it requires that you not perform simple surface mining of the same glacier body that your living in so as to avoid damaging your own habitat.

Construction on the surface with arches, vaults, columns and other compression load bearing structures can provide the necessary radiation protection without any of these issues. The same thin membrane pressure vessels inflated inside these protected spaces will be necessary but this is unavoidable and a wash. Also note that some posters have erroneously claimed that a single massive pressure vessels is more efficient then many small ones, this is a common error in thinking that the pressure vessel mass scales only with surface area, in actuality it scales with volume due to a large vessel needing a thicker wall. Given the inherent danger, I would say death-trap-ishness, in a single pressure vessel the interconnecting of many individual pressure vessels is certainly the way to go.

Note that a livable habitat is going to consist of a LOT more mass in equipment, life-support and otherwise beyond the pressure vessel, even a pressure vessel made 100 percent from local materials will need nearly the same amount of vital equipment to shipped in. This is the flaw in most space-cadet style housing solutions, they pretend that they are making log cabins in which just walls and roof are all that's needed and that they are saving 90 percent of the shipment mass from Earth.

I think you're confusing pressure vessels with making things gas-tight. "Arches, vaults, columns and other compression load bearing structures" won't help at all because your building will not be under compression at all. It will be under tension. The atmospheric pressure inside will try to push things apart form the inside.

Also a few feet of regolith on top won't help much against an atmospheric pressure of 10 tons per square meter trying to push things apart from the inside. You'd need to pile 10 tons of regolith per square meter on top of your building to counter the atmospheric pressure inside. Regolith has a density of about 1.5 g/cm^3, so in Mars' gravity this would be a layer of 20 meters (about 65 feet) thick. Only if you would add even more on top your structure will start to come into compression and you'll start to need arches, columns etc. Until then it is under tension and will try hard to explode from the inside.

Cracks in rock in a cave or tunnel aren't a problem, a thin membrane to prevent gas from escaping is easy, but there is no such thing like a "thin membrane pressure vessel". In a cave the pressure would be countered by the weight of the rock above and around it. If you don't have that weight you have to counter the pressure by tension in your pressure vessel and this not going to be a thin membrane then or bricks, or anything short of steel or aluminum, or massive reinforced concrete.

And yes, you need more than just pressure vessels to live in, but they're the biggest things you need and if they fail you won't have any time to fix things, because you will be dead immediately. They are the first and most crucial thing you need. And if you want to live and grow food in them, they need to be big and you need many of them and they need to be safe.

Also a few feet of regolith on top won't help much against an atmospheric pressure of 10 tons per square meter trying to push things apart from the inside. You'd need to pile 10 tons of regolith per square meter on top of your building to counter the atmospheric pressure inside. Regolith has a density of about 1.5 g/cm^3, so in Mars' gravity this would be a layer of 20 meters (about 65 feet) thick. Only if you would add even more on top your structure will start to come into compression and you'll start to need arches, columns etc. Until then it is under tension and will try hard to explode from the inside.

1.5g/cm^3 means 1.5t/m^3. So more like 6.67m thick for 10t. Mars gravity is only 0.38g, so more like 17.54m. Maybe it would make sense to reduce the pressure in the hab.

For a bigger habitat the excavated regolith for the cover will be smaller relative to the total excavated regolith. So I think bigger (or better deeper) is better. In theory.

Yes, the atmosphere being 96% CO2, 2% nitrogen and 2% argon (roughly) means you will accumulate quite a bit of both. Still, to replenish your internal atmosphere you will have to store them in high pressure vessels. In the long run you'll have reserves, but for quite a while having a nice atmosphere in your habitats will be too precious to vent them. Also nitrogen is important for plants, you'll tend to not waste it.

It seems we have a misunderstanding. I am not suggesting wasting anything. We have a large habitat with breathable air. We have a house that is not pressurized by itself because it does not need to be. Opening the window exchanges air with the larger cave which is closed. Nothing is wasted unless you see pressurizing a large cave with breathable air is waste.

OK, so a big buffer of pressurized volume to dump excess heat into. I would guess just dumping into a more remote part of the glacier with water loops and heating the ice there a bit would be easier, but on the other hand you will be carving out bigger and bigger caves all the time anyway.

There are clear advantages to having enormous spaces. A not-so-obvious advantage is that all other things being equal, the greater the enclosed volume, the slower the rate of change in the proportions of the gases in the (well mixed) breathable air out of any given source of imbalance, giving more time for the ECLS systems to respond and correct that O2/CO2 imbalance. Having more time to react is generally a good thing in closed loop control systems. Every contribution to robustness adds up and after some point where every subsystem is made robust with relaxed tolerances you can have a habitat design that can be surprisingly safe. That would be the way to go, I think.

OK, so a big buffer of pressurized volume to dump excess heat into. I would guess just dumping into a more remote part of the glacier with water loops and heating the ice there a bit would be easier, but on the other hand you will be carving out bigger and bigger caves all the time anyway.

That's the idea. As I said this should be designed to get rid of excess heat without requiring any active technical devices. Plus the children can go outside and play. -15°C and dry air are ok without much wind. You could make snow, too.

There are glaciers big enough that you could build a whole 1 million people city that way and not use much of its volume. Though I believe this would be only one of different types of habitat.